[technet.microsoft.com...]
According to the info above, you'll need to use /r

I'm not sure what information might be displayed, but bad sectors on more than one track and you absolutely need to replace the hard disk. Personally, I would do so if there was more than a single bad sector, but maybe that's just me.

Kaled.

As kaled suggested I'd also try

chkdsk /r

first. However, once a sector is marked bad it won't be used any more, so you can continue to use the drive in most cases. I would certainly consider a new drive if possible.

Another utility I've had success with is the SpinRite product. It's not free, but my license has paid for itself many times over. I use this program for HDD maintenance and recovery.

Thanks for the responses. I'm running /r and it's taking an age.

I'll certainly consider a new HD.

OP - If you get to a point where you can't boot windows, consider an external USB hard drive enclosure.

I've had a lot of luck retrieving data as long as it isn't encrypted. You remove the HD and put it in the HD enclosure.

You can run into problems when viewing the drive in vista when you get into the documents and settings folder. You just need to allow Vista to take control of the folder.

If you aren't familiar with handling drives, I would only do this as a last resort.

Is trusty, but old, chkdsk/f good enough?

In my experience, you can have serious errors on your hard drive that chkdsk won't see.

In addition to backing up my data to an extra drive on my machine, I clone my main drive to a set of external drives... and Acronis (which I use for cloning) was reporting regularly that it couldn't read certain sectors on the main drive. The situation got worse over time, but chkdsk continued to report the sectors as OK.

I finally downloaded the manufacturer's diagnostic tool, which also gave the drive a passing grade, but it did report "weaknesses" where Acronis was having trouble. I got rid of the drive for other reasons, and, fortunately, the bad sectors were in an area where there was no data, so I was able to substitute one of my clones with no problems since. I have lost all trust in chkdsk as a result, though. It gave no indication of any problem at all.

I'd like to know more about SpinRite. I was considering it at the time, but ended up not needing it, at least not then. I don't know whether it would be a luxury to have it hanging around just for an emergency or not.

Way back, in the FAT days, I used to run Norton Utilities and Norton Disk Doctor regularly for disk maintenance, but that was pre-Symantec and pre-NTFS. Is there any point in any regular kind of disk/file maintenance, aside from defragging, with NTFS?

The situation got worse over time, but chkdsk continued to report the sectors as OK...
fortunately, the bad sectors were in an area where there was no data...
I have lost all trust in chkdsk as a result

I'm the brutal one round here that doesn't believe in subtlety...

1. If you were using /f, chkdsk wasn't scanning for bad sectors
   
2. Since you weren't scanning for bad sectors, there was zero possibility of finding them in unused areas of the disk.
   
3. Your loss of confidence in chkdsk resulted from your own lack of understanding.
   

Drive imaging software necessarily scans every sector of a drive whereas a basic error check simply looks for cross-linked files, etc.

It's also worth noting that a medium-level program (such as chkdsk, I think) may not detect failing sectors since such programs normally only go as far as determining whether data can be read or not - they don't count the number of attempts required or the number of corrected errors, etc. Also, I don't think such information is available without talking directly to the drive (i.e. bypassing the bios and/or drivers) but I'm not certain.

I believe some drives automatically detect failing sectors and move the data transparently to other physical sectors (remapping the drive) but I don't bother to follow hardware developments these days, so I'm not sure.

Kaled.

If you were using /f, chkdsk wasn't scanning for bad sectors

kaled - Thanks for the amplification on this point. I'd just copied and pasted the OP's question, without further editing, and I don't actually have a record of what I did at the time I ran my scans.

As I review the reference I would have used (O'Reilly - Windows XP in a Nutshell), and knowing how I generally approach these things, I would have scanned the c: drive first with no parameters, just to get a report, and then, if I'd gotten a positive, would have run it with the /r parameter ("locates bad sectors and recovers readable information"). I may have not gotten a positive and subsequently decided, after further cloning problems, to run with /r anyway. I assume if there were any failed (as opposed to failing) sectors, with this approach, chkdsk should have found them.

chkdsk parameters aren't anything I use often enough to commit them to memory, though this discussion will help with that. ;) I've got a pencil mark highlighting the item in the index to the O'Reilly book, and that's about it.

This comment of yours tells me a lot, and may well relate to the situation of the original post....

It's also worth noting that a medium-level program (such as chkdsk, I think) may not detect failing sectors since such programs normally only go as far as determining whether data can be read or not - they don't count the number of attempts required or the number of corrected errors, etc.

A question about marked bad sectors, which I hope doesn't take this thread off topic... The following comment in the Microsoft notes makes me ask how does drive imaging software deal with marked bad sectors?... and what mechanisms are involved when a clone is then made to a disk that itself has marked bad sector? I assume that all marked bad sectors are somehow observed by "the system", and that a clone is not actually a clone. I am talking about what they do call "cloning", btw, and not imaging and restoring.

From the Microsoft Troubleshooting documentation...

Bad sectors reported by Chkdsk were marked when your volume was first prepared for operation. The fact that they are marked as bad means that the system prevents the disk from using them, so previously identified bad sectors pose no danger to your data.

If a sector-by-sector copy is made and the target drive has bad sectors...

If the target drive can remap bad sectors there should be no problem, otherwise, the software will have to interpret the data (i.e. have knowledge of the filing system) and make changes.

Personally, I have suffered very few hard drive failures, I put this down to staying away from certain manufacturers but also staying away from cutting-edge drives. As a rule of thumb, I tend to stay 18 months to 2 years behind all cutting edge technology - this is good for the pocket as well as reliability.

These days, it's easy to imagine a drive having at least 1 Gig of flash memory to be used exclusively for replacing bad sectors but I don't know if any manufacturers do this.

Kaled.